The Frontiers in Astronomy and Space Sciences published a Magnetohydrodynamical (MHD) numerical study on the velocity distribution associated with the extreme ultraviolet (EUV) disturbances in the corona just a few days ago. In the study, Dr. MEI Zhixing from Yunnan Observatories of the Chinese Academy of Sciences and his colleagues presented a 3D MHD simulation of eruptive magnetic flux-rope, emphasizing several structures inside the velocity field of eruptive source region.

Coronal disturbances in extreme ultraviolet (EUV) during the coronal mass ejection (CME) eruptive events have been observed and simulated extensively during past decades. MEI Zhixing and his colleagues carried out a 3D MHD numerical simulation based on the flux-rope model of solar eruption to the structures of the velocity field in the eruptive source region.

Their results highlight that the velocity distribution of the lower atmosphere develops complex structures at the flanks of eruptive flux-rope. Two streams of plasma exist in the lower atmosphere of the eruptive source region, divided by a 3D velocity separatrix (VS). Outside the VS, plasma moves outward to the expanding fast shock (FS) front. Inside the VS, the plasma moves toward the center of the source region. The interaction of two streams of plasma flows has invoked two types of vortexes and the slow shocks (SS) near the VS. In the first type of vortex, the plasma converges toward the vortex center. In the second type, the plasma spreads out from the center. 

To directly compare with realistic EUV observations, they use the forward modeling method to create synthetic Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) images for different wavelengths. In synthetic images, the EUV disturbances appear as a 3D dome, including the FS, the helical current sheet and the flux-rope.

Furthermore, they also deduce the plasma velocity field by utilizing the Fourier local correlation tracking method on the synthetic images. However, they do not observe the VS, the SS and the two types of vortices in this deduced velocity field.

Contact
MEI Zhixing, YNAO, CAS
meizhixing@ynao.ac.cn